460 ZOOLOGY. 



Loncheres, Isotkrix, Mesomys,^ Echimys, Nelomys^ and Aidacodon, belong to 

 this section of hystricines. 



Several fossil remains of this sub-family have been found in the caverns 

 of Brazil, and wliich were described as species of Aulacodon, Nelomys, and 

 Echimys ; but the characters by which these genera are distinguished being 

 so difficult to trace out upon fragmentary remains, the genus Caiterodon 

 has been proposed, to unite them all. Besides, there is another species 

 referred to the genus Loncheres, and still another to the genus Phyllomys, 

 and a third, Lonchoj^horiis, has been established. Its aflfinities place it 

 between Echimys and Loncheres, and it existed only during the period of 

 the diluvium. 



/Sub-fam. 5. Dasyproctina, are characterized among the other hystricines 

 by semi-rooted molar teeth, arranged in parallel series. The feet are 

 constructed for running, with five toes, or three only to the hind feet, 

 terminated by sub-solid nails, which are but little arched. The tail is 

 rudimentary; the bod};- clothed with hair only, there being no admixture 

 of spines. This sub-family includes two living genera. 



The genus Ccelogenys contains but one well established species, the 

 Paca. The zygomatic arch is very well developed and of great depth, the 

 incisors slender, and five toes to the fore and hind feet. The Osteopera 

 'platycephala, of Harlan, is referred to this species. Fossil remains of one 

 or more species of the present genus have been discovered in the Brazilian 

 caverns. 



The genus JJasyprocta (aguti) has but three toes to the hind feet ; the 

 limbs are long and slender ; the crown of the molar teeth rounded with a 

 single fold of enamel, and four or five isolated grooves surrounded by 

 enamel. The hinder parts of the back are covered with very long and 

 coarse hairs. Several species of this genus are known in the actual fauna; 

 the fossil remains of others are found in the Brazilian caverns. 



Suh-fam. 6. Hystricina proper, or porcupines, are provided with rooted 

 or semi-rooted molar teeth ; the feet are short, the number of toes variable, 

 andithe body more or less armed with spines. 



The porcupines are divided into two sections. One is composed of 

 species living upon the ground and seeking shelter in burrows which they 

 themselves form. They have five toes both to the fore and hind feet ; the 

 soles of the feet naked and smooth ; the molar teeth semi-rooted and 

 arranged in parallel series. The species of this section (Philogcece) are 

 confined to the old world. Those of the other section {Philodendne) are 

 peculiar to the new world. They have climbing habits, and live almost 

 entirely in trees. Their feet are usually provided with but four toes, and 

 these are nearly equal in length, armed with long, compressed, and curved 

 claws; sometimes, however, the hind feet have five toes. The soles of the 

 feet are thickly studded with minute, depressed warts. 



The porcupines of the new world, the Philodendrce, are divided into 



three genera, Chcetomys, Cercolahes, and JErethizon. The first contains 



but one species, from Brazil ; the second is more numerous, and is more 



widely spread. One of the species, C. villosus {pi. 113, fig. 3 a), inhabits 



664 



